Since it looked like an interesting topic in game, I am going to post here how to use those 3-4 mouse buttons in Istaria.

Those mices are fantastic because they let you i.e. to strafe and do other things that with just two mouse buttons would require additional keyboard efforts. And you KNOW dragons are lazy, didn't you?

Steps:

1) Download Autohotkey from http://www.autohotkey.com/
Just in case you were wondering, it's free and GPL license.
Any version should do for what we need.

2) Install it and run it.

3) It will ask if you want a demo script created. Click YES.

4) Run it and check if you see a green "H" shaped icon in the tray bar.

5) Right click it, go to "Edit this script". Some ".ahk" file should appear.

6) Go to the bottom and add (paste) the following verbatim:


#IfWinActive ahk_class igWin32WindowClass
XButton1::[
XButton2::]
#IfWinActive

7) Close and save the thing.

8) Right click the icon again and select "Reload this script" to let Autokey re-parse the modified script.

9) Go in Istaria => Blue gem => Options => Keybindings

10) Set the things you desire. In my case it was "Step left" and "Step right" to add strafe as follows.

If you look at the above script blurb you'll notice "XButton1::[".

That means: assign mouse extra button 1 (aka mouse button 3) the "[" keystroke.

So if you mapped the mouse button 3 to "[" as I shown above and assign Step Left to "[", then the game will react to mouse button 3 like you pressed "[" and you will strafe left.

The "rules" are easily expanded: just add more

XButtonN::X

where N is the additional button on your mouse and place some unique keystroke X after the double colons "::" ("[" in the example).

Just be careful not to alter the beginning of the script because Istaria requires those non standard settings to work with this program.

Have fun,
Vahrokh the Ancient